214 LAXD AND FRESH-AVATER SHELLS OF N. A. [PART IV 



99. G. nigrina, Lea. 



Melanin nigrina, Lea, Proc. Acad. Nat. Sci., p. 80. April, 1856. 

 Goniobasis nigrina, Lea, Jour. Acad. Nat. Sci., v, pt. 3, p. 302, t. 37, f. 137, March, 

 18G3. Obs., i.x, p. 124. Binnev, Check List, No. 177. 



Description. — Shell smooth, small, conical, rather thin, nearly black, 

 polished ; spire somewhat elevated ; sutures impressed ; whorls regu- 

 larly convex; aperture small, ovate, angular above, dark purple 

 within; columella incurved, purple. 



Operculum dark brown, the polar point being low down and near to 

 the left margin. 

 Habitat. — Clear Creek, Shasta Countj-, California; Dr. Trask. 

 Diameter, -23; length, -67 of an inch. 



Observations. — A number of good specimens, with their opercula, 

 were sent to me by Dr. Trask. In form, size and color this species 

 is very like to Melania semicarinata. Say, from Georgia and 

 South Carolina. It may be distinguished at once by not hav- 

 ing the carination of that species, which is usually strongly 

 marked. It is not quite so high in the spire, and the aperture 

 is more rounded at the base. In all the specimens of nigrina, 

 which I received, the apex is worn ofl'. In the half grown ones I 

 can see no disposition to carination or plication in the upper whorls. 

 I should suppose that in perfect specimens the number of whorls 

 would be found to be about seven, and that the aperture would be 

 about the third of the length of the shell. In some of the specimens 

 there is a disposition to put on a few, fine strise, and in most of them 

 there is a very small, angular line running below the suture. I am 

 not acquainted with Dr. Gould's Melania silicula and bulbosa from 

 Oregon, described in the Proc. Boston Soc. Nat. Hist., July, 1847; 

 but from the descriptions I have no doubt that they are different from 

 both species therein described. — Lea. 



The upper whorls of this species are sometimes plicate. The 

 shell is like silicula in form, but is rather more cyliudrical, of 

 a darker color, shaded with red internall}'. It is particularly 

 distinguished by the carinated upper whorls. 



This is not the nigrina of Reeve's Conch. Icon., that species 

 being the nigrocincta, Anth., as Mr. Eeeve states in his "errata." 



